Scientists have made a groundbreaking discovery about the movement of Earth’s crust. Seismic mapping has revealed an ancient slab of crust buried beneath the Midwest, causing rocks from across the continent to be sucked down into the mantle. The slab, known as the Farallon plate, broke off 20 million years ago and is responsible for a process called “cratonic thinning.” This thinning results in large parts of North America losing material from the underside of their crust.
Researchers used a high-resolution seismic imaging technique to map what lies beneath North America. The technique allowed them to extract information about physical parameters underground, providing insights into the movement of the Farallon slab and its impact on the continent. According to study lead author Junlin Hua, “A very broad range is experiencing some thinning,” indicating that the effects of the Farallon slab are widespread.
The researchers found that the drips result from the downward dragging force of the Farallon plate, which has created giant “drips” hanging from the underside of the continent down to about 400 miles deep in the mantle. These drips are located beneath an area spanning from Michigan to Nebraska and Alabama but appear to be impacting the entire continent.
The discovery was possible thanks to a wider project led by Hua to map what lies beneath North America using full-waveform inversion. This technique uses different types of seismic waves to extract information about physical parameters underground, providing a better representation of the zone between the deep mantle and the shallower lithosphere.
While the effects of the Farallon slab will not be immediately visible at the surface, researchers believe that it may stop as the slab sinks deeper into the lower mantle. The findings could help piece together the puzzle of how Earth came to look the way it does today, understanding how continents are formed, broken, and recycled.
Source: https://www.livescience.com/planet-earth/geology/north-america-is-dripping-down-into-earths-mantle-scientists-discover